Fuel oil



Patented Sept. 15, 1931 UNITED STATES PATENT OFFICE STERLING H. DIGGS, OF CASPER, WYOMING, ASSIGNOR TO STANDARD OIL CO HPANY,

- OF WRITING, INDIANA, A OORPORATION OF INDIANA FUEL OIL No Drawing.

divides into a lower aqueous layer consisting mainly of dilute sulfuric acid. and a supernatant layer of oily and tarry substances.

In converting the acidsludge tar into fuel oil, for example, railroad fuel oil, it has heretofore been the practice to reduce the tar 5 with steam so as to recover valuable naphtha bottoms therefrom and to cut-back the residue to the desired viscosity with a cheap diluent to give a fuel of satisfactory viscosity. Suitable cut-backs are high sulfur gas oil, and reduced high pressure tar.

Fuel oil produced in this manner is per se satisfactory for combustion in locomotive and other burners. It has, however, an outstanding disadvantage in that on mixing with certain standard fuels of the same gen eral type, an excessive quantity of bottom settlings is produced. Thus, when such a fuel oil is mixed with a railroad fuel derived from a residue containing large quantities of waxy and asphaltic materials, the amount of bottom settlings from the mixture may amount to several times the amount which would be anticipated from the bottom settlings of each of the .constituents. An example of such a ,fuel oil is that produced from reduced pressure tar from Burton 0r Burton- Clark cracking stills. This disadvantage has heretofore prevented the utilization of sludge tar for the production of commercial fuel because of the certainty that in actual practice, the two kinds of fuel would become mixed in supply tanks and storage tanks and the burners and feed-pipes would become choked. 1 f

It has now been discovered that this difliculty can be completely avoided by conduct- 4 ing the reduction of the slude tar under such conditions that the temperature exceeds 500 and preferably attains temperatures between 550 and 600 F. The result of this high tem -s ecifications results.

Application filed. January 16, 1928. Serial N0.'247,284.

perature seems to be the breaking up of oxygen and sulfur compounds present in the.

sludge tar, which apparently were responsible for the excessive settling from the mixed fuel oils. Hi her temperatures may be employed, if desired, but are not necessary for the accomplishment of the desired result.

The invention will be readily understood from the following description of a. preferred example. Sludge tar derived on separation from the aci layer and containing about of naphtha bottoms is heated to a high temper-' ature and the naphtha bottoms recovered and condensed. The heating. may be effected in a pipe still or in a shell still. When the latter is employed, it is preferred to inject a small amount of steam so as to give enough agitation to prevent the settling of insoluble matter on the bottom thereof. During this heating, the temperature is caused to rise above 500 F. and preferably between 550 and 600 F. The viscosity of the residue is relatively unimportant and it varies considerably, for example, from 300 to 1000 furol at 122 F. The steam-reduced taris now out back by addition of an oil of less viscosity until a fuel oil meeting the For railroad fuels, t e viscosity must usually not exceed furol at 122 F. and it is preferred to reduce' the viscosity to below 40, for example, 35 or lower. The amount of diluent is relatively small, for example, a mixtureof 40% of oil having .aviscoslty of.l0- and 60% of an oil having a viscosity of 600 will" have a viscosity of about 35.

In actual practice, it is desired to blend the reduced steam tar or bottoms with other fuel oils, for example, a fuel oil having a viscosity of about 25 furol at 122 F. de-

Burton or v water, hydrocarbon constituents from the aqueous aqueous acid solution, heating said hydrocarbon mixture to expel the added hydrocarbons of low viscosity, raising the temperature to between 500 and 600 F., and cutting-back the residue with fuel oil constituents of relatively low viscosity to give a blended fuel of desired viscosity.

2. The method of producing fuel oil from acid sludge which consists in adding thereto. a h drocarbon oil of low viscosity and heating with agitation, separating the acid solution, heatin said hydrocarbon mixtureto expel the ad ed hydrocarbons of low viscosit raising the temperature to between 500 an 600 with a residual fuel from a cracking operation of the Burton type, to give a blended fuel of desired viscosity.

3. The method of making fuel oil which consists in separating a hydrocarbon layer conta' oxygen and sulfur compounds from aci slu ge, heating said layer of hydrocarbon compounds to a temperature between about 500 and about 600 F., thereby driving OK the more volatile constituents,

and cuttin -back the residue to a desired viscosity with fuel oil constituents of relatively low viscosity.

4. The process of converting acid sludge tar containing insolubilizing oxygen and sulfur compounds into an. oil which may be mixed with fuel oils without mutual precipitation of objectionable slud ge compounds comprising heating said acid tar above a temperature of about 500 F. and not substantially above 600 whereb said oxygen and sulfur compounds are ecomposed and then reducing the viscosity of the resulting oil by adding a small proportion of a low viscosit fuel oil.

TERLING H. DIGGS.

and mixing the residue 

